This invention relates to power control in radio communications systems such as CDMA cellular telephone systems.
xe2x80x98Outer loopxe2x80x99 power control is required in a CDMA system to set an appropriate target for the xe2x80x98inner loopxe2x80x99 power control loop which is just high enough to achieve the desired quality of service (QoS). This target point value will vary as a function of channel propagation (e.g., dispersiveness or user speed). Without effective power control, users perceived QoS will be severely degraded or network capacity will degrade (as a result of excess power transmission when exceeding desired QoS).
In particular, dynamic outer-loop power control is required in a CDMA system in order to adjust the Eb/No (the ratio of energy per bit to noise power spectral density) target point for an inner power control loop in order to track changes in channel propagation in an attempt to maintain constant QoS.
Future generations of cellular telephone services such as the proposed Universal Mobile Telephone System (UMTS) will offer a plethora of different services, each with quite different QoS requirements in terms of delay, bit error rate (BER) and frame erasure rate (FER). This represents a challenge to mobile radio equipment manufacturers who must therefore design their products to be fully adaptable to these various requirements.
Traditional methods for performing outer-loop power control, such as those based on the xe2x80x98sawtoothxe2x80x99 algorithm employed in existing CDMA networks (e.g., the IS-95 cellular standard), are not appropriate for all service types. This is especially true of low FER or high delay services (e.g., video)xe2x80x94which are to be deployed in next generation networks across the world.
In accordance with a first aspect of the present invention there is provided an apparatus as claimed in claim 1.
In accordance with a second aspect of the present invention there is provided a method as claimed in claim 6.